Unlike cupcake vs. muffin, toast vs. spam takes on a more creative route. Smelling of toast for days, a team created a little "toastvertising" against spam using 220 pieces of toast. Thankfully it wasn't the other way around, as the smell of spam for days is quite worse than any email selling b!g er3ct!0n_s.
My roommate in college would not buy Spam. He was too cheap for that. He instead would by - Treet. Imitation Spam - http://en.wikipedia.org/wiki/Treet